Poor weather conditions may have forced a bus to detour from its normal route before it rolled several times near Mexican Hat, San Juan County, killing nine people and injuring 20 others.

Utah Highway Patrol Sgt. Ted Tingey said Corporate Transportation 'N Tours was investigating whether one of its buses taking a group of skiers from Telluride, Colo., to Phoenix was forced to take U.S. 163 Sunday night because of road closures, bad weather, or if the bus was on its intended route.

The bus rolled 10 miles north of Mexican Hat Sunday night.

"It looks like the bus failed to negotiate a turn," Roden said Monday. "It rolled several times."

Pictures of the crash provided by the UHP showed the bus' roof was sheared off and debris scattered all around it. The 51 passengers inside the bus were tossed around and many were ejected, Utah Highway Patrol trooper Cameron Roden said.

The number of people killed rose to nine Monday when a woman taken to Saint Mary's Hospital in Grand Junction, Colo. died as a result of her injuries.

Monday night, the names of the victims who died, all of them Arizona residents, were released. The youngest victim was a 12-year-old girl, and the oldest was 67.

Many of the victims were teenagers from Arizona high schools, including Erica Sheffey, a junior at Deer Valley High School, and Marc Rasmussen, a senior at the school.

"I am so sorry to have to convey to you that at this time two of our students perished on the horrific bus crash in the Four Corners area," Deer Valley principal Barbara Dobbs said in a letter posted on the school's Web site Monday night. "Our thoughts and prayers go out to them and their families."

Dobbs said grief counseling would be provided to students at the school who need it.

The bus was part of a 16-bus caravan carrying a group that had booked a trip through Phoenix-based Alpine Ski and Travel, according to the Arizona Republic. The bus that crashed detoured from the rest of the group in Colorado, the man who runs Alpine told the Republic. The other buses returned to Arizona safely.

People who said they were on the other buses posted comments on the Arizona Republic's Web site Monday, saying the road conditions driving home were very treacherous and describing the trip as "scary."

The driver of the bus, 71-year-old Lotan Welland of Gladwin, Mich., was transported to a Kayenta, Ariz., hospital. Victims with injuries ranging from critical to minor were taken to various hospitals throughout Utah, Colorado, New Mexico and Arizona.

At least two patients were flown to Salt Lake-area hospitals.

As of Monday afternoon, Intermountain Medical Center in Murray reported having one male victim, still in critical condition. University Hospital reported two, a female in critical condition and a male whose condition was not available. St. Mary's Hospital in Grand Junction, Colo., reported receiving 10 of the crash victims, but did not have any additional information available.

Crash victims were scattered throughout the scene, which looked like a "war zone," said Rick Bailey, emergency services director for San Juan County.

"We called every available first responder we had in the county last night," Bailey said.

At least nine ambulances were dispatched from the San Juan County area and three more from the Navajo Nation in Kayenta and Red Mesa in Arizona and Shiprock, N.M.

Bailey reached the scene at about 9:45 p.m., by which time another bus already had arrived at the scene. By about midnight, passengers who did not require medical attention were able to leave. Road conditions at the time Bailey arrived were wet but apparently not icy, with the temperature somewhere between 35 and 40 degrees.

Despite seeing bodies scattered and a bus with its top torn off, Bailey, a former EMT, described a crash scene that was calm, with uninjured passengers helping others in need. "There was quite a good, orderly fashion with that," he said.

Bailey said the section of road where the bus veered off between Mexican Hat and Bluff has several sharp turns, but that it's not an area where there are frequent crashes. He said a meeting may be coming with the Utah Department of Transportation and county officials there to discuss the potential dangers of that road.

"We'll talk about that with them, to see if any improvements can be made," Bailey said.

San Juan County emergency responders, particularly the volunteers at the scene, were restocking ambulances Monday and otherwise regrouping from the emotional trauma. Some of the rescue workers may need some counseling, Bailey said.

"It's tough for paid professionals to see that and deal with that," he said. "We want to make sure they're taken care of."

UHP investigators were back at the remote crash site Monday, trying to glean more about the cause. The weather was bad, but the UHP said that was not likely the primary cause of the rollover.

"We are still looking at the driver being the cause and not negotiating the curve," Roden said.

The UHP reported the only seatbelt on the bus was on the driver's seat.

The National Transportation Safety Board is sending a team of seven investigators to the scene of the crash. Agency spokeswoman Bridget Serchak said it could be at least a year before a final report will be released on the probable cause.

"It just depends on all the different factors involved," she said.

In a statement Monday, Corporate Transportation 'N Tours' Bruce Neuharth said it was investigating the crash.

Passengers who did not require hospitalization were picked up by another bus and taken to their final destination in Arizona, Neuharth said.

"On behalf of everyone at Corporate Transportation 'N Tours, I want to express our sympathy and prayers to the passengers and their families during this time of sadness and loss," Neuharth said.

Investigators said there are problems with the bus' manifest logs, making it difficult to immediately ascertain a maintenance history or where the bus had been.

Utah Department of Transportation spokesman Nile Easton said federal safety data show the company has a sound safety record. The company, which runs between 70 and 80 buses, was found in "satisfactory compliance" with safety regulations during a review a year ago.

The company reported 10 accidents in the last two years, six of which involved injuries but no fatalities.

"Overall, they have a pretty good safety record," Easton said.

Identities of people who died from crash

The identities of the fatal victims of Sunday's bus crash near Medicine Hat, all residents of Arizona, have been released. They are: